Method of orienting whipstocks



July 2, 1935. G. L. KoTHNY METHOD 0F ORIENTING WHIPSTOCK Filed Sept. 27.1933 Patented July 2, 1935 l A I y UNITED sTATEs PATENT OFFICE METHOD FORIENTING WHIPSTOCKS Gottdank L. Kothny. Stratford, Pa., assignor toSperry-Sun Well Surveying Company, Philadelphia, Pa., a corporation ofDelaware Application September 27, 1933, Serial No. 691,253

4 Claims. (Cl. 255`1) This invention relates to the drilling of wellsing the whipstock by orlenting the upper er .d of and has particularreference to a method of the drill stem if the drill stem is made ofsecorienting a whipstock designed to guide a drill tions which are linedup with each other in a in a definite direction as is necessary, forexknown fashion. Attempts have been made to so 5 ample, in straighteninga crooked well. orient whipstocks under the assumption that if 5 As iswell known, many wells, particularly those a. certain point at the upperend of the drill stem, produced by rotary drilling, deviate veryconsidconsisting of aligned sections, will point north erably from thevertical at even moderate diswhen a corresponding point at the lower endof tances below the surface, such deviations being the drill stem pointsnorth, assuming the drill apparently due to lack of uniformity in thes'oil Stem to be straight, then this correspondence in l0 through whichthe drill is passing and being parazimuth of the two points will bemaintained ticularly noticeable in the case of rotary drilling when thedrill stem is located within a crooked since the rotation of the drillstemappears to bore hole. This, however, is incorrect. Due to promotethe production of a tortuous hole. If the effect of tortuosity eventhough there iS n0 a bore hole deviates to a substantial degree fromtOrSiOnal Stress UDOn the Stem about its axis at l5 the vertical it mayentirely mlssthe locality which any location along its length.nevertheless. coris believed to contain cil. Once a. bore hole beginsresponding DOintS defined es above Will not point to deviate from thevertical little can be done in in the same direction. The result of suchorientathe way of controlling the drill from the surface tion processeshas. 0f COlllSe. been an imDrODel to cause it'to become straight.Accordingly, it location of ,WhiPStOCkS in View 0f the llnWaI- 20 is thepractice to insert within the bore hole a ranted assumDtiO. 85 t0maintenance 0f relawhipstock having a guiding surface at an angle tiveorientations corresponding t0 those Occurl'ing with the axis of the borehole to direct the drill when the Stem is straight. in the" reddirectiontoreach its objective. Ob- .It is the object of the presentinvention to viol..` v .t is necessary to properly orient the provide amethod of orienting 9, whipstock with- 25 whipsitck and check theorientation tov insure in a crooked bore hole in which the angular thata proper correction of the direction of the POSitlOn Gf the WhlDStOCk i8adjusted by the turnbore hole will be made. ing of the upper end of adrill stem by which it The orientation of a whipstock necessarily inissupported. In accordance with the invention,

volves a knowledge of the path of a bore hole so however, a properorientation of the whipstock 30 that a preliminary survey must be madeto find is assured, within, of course, the limits of error the directionand position of the lower end of arising because of the algebraicaccumulation of the hole. errors in lining up the various drill stemsections.

Various methods of orienting whipstocks are It is a further object ofthe invention to proknown,atypical one being described in the transvidesuch method of orienting a whipstock in 35 actions of the Institute ofMining and Metalwhich a check is provided upon its position, this lurgy(1911-1912, pages 481 to 489). The methbeing eflected by includingwithin the length of ods such as that described in this publication arethe drill stem at its lower end a surveying instrucomparativelydifficult to carry out and are not ment capable of indicating accuratelythe "4o likely to lead to an accurate positioning of the azimuthalposition of the whipstock while the 40 whipstock, unless a check of thetrue position of whipstocir *s being lowered and set in place. The thewhipstock is made by means of an accurate necessity for accuracysubstantially requires that well surveying instrument of gyroscopictype, this well surveying instrument should be of gyromagneticinstruments being affected by magnetic scopicharacter.

materials, casings, etc. Carrying out any of the Other objects of theinvention will be apparent 45 known processes, however, is quitediiiicult by from the following description read in conjunreason of thevarious manipulations involved, so tion with the accompanying drawing inwhich: that they are impractical. Fig. l is a diagram showing thoconsiderations In the process described in the above publicainvolved incorrections for tortuosity;

tion, the whipstock is lowered on the end of a Fig. 2 is a diagrammaticelevation showing the so i drill stem. being secured to the drill stemby assembly of the drill stem, well surveying inmeans of soft metalrivets which can be sheared strument, and whipstock prior to setting;and of! to eventually leave the whipstock in position. Fig. 3 is a viewshowing the type of record Since this is the desirable manner oflowering made by a preferred form of surveying instruthe whipstock itsuggests the possibility of orientment. 65

Referring rst to Fig. 1 there is illustrated therein the position whichmight be assumed by a hypothetical smooth cylindrical drill stem withina bore hole whose center line is a curve in three dimensions; that is.one which does not in its entirety lie within any plane. The usual pathof a bore hole formed by-rotary drilling is a curve of this character,the rotation of the drill stem promoting the formation of such tortuouspath.

The eifective rotation of a drill stem a due to tortuosity may bedetermined by considering a hypothetical line e drawn along thecylindrical surface of the drill stem parallel to its exis c when thestem is straight. When the stem is lowered in a crooked bore hole theazimuthal position of this hypothetical line relative to the center linewill vary depending upon the shape of the hole. If every portion of thestem is to be without torsional strain we can correctly assume that, ifat any point we out the stem by a plane perpendicular to the centerline, then the hypothetical line e at its intersection with the planewill be parallel with the center line c at the intersection of the planeand center line. This will be recognized as the obvious condition forabsence of torsion in a cylinder.

Choosing rectangular axes such that the positive direction of the :caxis is horizontally north, the positive direction of the u axis ishorizontally east, and the positive direction of the z axis isverticallydownward, the center line of the bore hole (or drill stem) maybe expressed by parametric equations:

' a:=:c(s) ll=ll(8) 2:2(8)

in which the parameter s is conveniently taken as the distance measuredalong the drill stem from the surface.

By then making certain approximations Justified by the fact that a drillstem will never have a small radius, of curvature, we obtain for theangle through which the azimuth of the hypothetical line has changed ina clockwise direction looking downwardly, if the bottom of the drillstem is assumed vertical,

dx dy:I dy dx Tand-en-csd dl s-0 the angle being measured in radians,and l being the length of the stem. v

Lf. the lower end of the bore hole is not vertical and terminates, say,at h of Fig. l, then it may be imagined as continued to verticality at mby being bent in the vertical plane of the inclination and thecalculation of made in accordance with the above formula to give thedirection f of the line-e relative to the center line c. The position ofline e at the actual end h may then be readily found by applying acorrection similar to that used for correcting the intercardinal errorof a gyroscope. 'Ihe results of the hypothetical case give, of course,the correction for tortuosity involved in the actual case.

From the above it will be seen that knowing completely the path of thebore hole, it is possible to calculate and4 make correction for theeffect oi tortuosity which, except for a complete knowledge of the pathof a bore hole, would lead to an unknown deviation of the position ofthe A whipstock from that which might oilhand be as- In .carrying outthe improved method, it is ilrst necessary to make a completedirectional survey of the bore hole. 'I'his must be done by the use ofsome instrument which is not in itself affected by errors due totortuosity, namely, an instrument which contains withinitself an elcmentfor indicating azimuth. Both gyroscopic and magnetic instruments wouldsatisfy this requirement; but the only type of instrument which is fullyreliable is a gyroscopic one due to the errors caused ind-magneticreadings by mineral deposits or the presence of magnetic bodiesartificially present in the bore hole. An accurate survey with no errorsdue to tortuosity or magnetism may be made by the type of instrumentdescribed in the patent to Williston and Nichols, Number 1.960.038,dated May 22, 1934. This instrument photographically records theposition of a gyroscope and 'a bubble at short intervals of time'corresponding to' relatively short distances along the path of a borehole. Such instrument may be lowered either on a wire line or a drillstem for the purpose of making the initial survey.

Following the complete determination of the path of the bore hole thetortuosity correction may be made by the use of the formula given above.

It may be pointed .out that a survey made by drill stem orientation is.of no use particularly in the present case because the effect oftortuosity which-it is desired to ascertain causes the determinations bysuch method of survey to be in error due to this same' eifect. In otherwords, the results of such survey would be in error so as to mask theeifeots of tortuosity. The result of the application of the aboveformula to the path calculated from such survey would lead to errore ofa magnitude corresponding to the magnitude of the tortuosity correction.

.Following the completion of calculations as above, there is loweredinto the bore hole at the bottom of a drill stem an assembly of the typeindicated in Fig. 2. This comprises a whipstock 2, which is shown asprovided with a chiselshaped lower end 4. The showing of this type ofwhipstock is to be understood to be conventional, since the whipstockmay be of any well known type involving, for example, an automaticarrangement designed to engage and hold the bottom of the whipstock atthe position of a Joint in a casing. The whipstock man' also be of thetype designed to be secured in' pince by cementing. The type ofwhipstock here nlustrated would be held in place -by being forced intothe soil at the bottom of the bore hole.

'I'he whipstock is secured by means of a soft metal rivet or pin 6 to anextension B of a setting tool l0 which is coupled by means of a sub,

I2 to the outer casing Il of a battery container which is indicated asfilled with a suitable number of batteries it. This casing is in turnconneoted by a coupling i8 to the outer` casing 20 of a surveyinginstrument of the type described in the above-mentioned Williston andNichols patent. This surveying instrument comprises three parisindicated at 22, including a gyroscope, a timepiece and a box levelwhich are arranged to be simultaneously photographed. by the use of amotion picture camera making successive exposures at suitably timedintervals.

Above the surveying. instrument there is provided a coupling 24 providedwith mud passages 26, to which coupling there is secured the lowermostsection 28 of the drill stem on which the apparatus is lowered.

'Ihe surveying instrument is oriented into a known position relative tothe whipstock so that, from the readings obtained in the instrument, thei...a1 position of the whipstock will be accurately known. This may beconveniently effected in the Williston and Nichols instrument. as willbe rear from Fig. 3, which represents the type of photographic recordmade in the instrument. On this photographic record there appear agyroscopic pointer 30 moving adjacent a scale 32, the lead 34, whichcarries current into the vertical gimbal ring of the gyroscope whichcarries the pointer 30, a watch 36, and a box level including theconcentric circular marks indicative of the inclination of theapparatus'by reason of the relationship relative to them of a bubble 40,and a line 42 which may be inscribed upon the surface of the box levelcover glass.

Either the line 42 or the lead 34 may be used as the zero of referenceof the scale 32, or the scale itself may be suitably marked with a zeroindication. Whatever this indication may be. it is brought into positionbearing a definite relationship to the inclined face of the whipstock.It will be understood, of course, that the box level occupies a fixedangular position in the casing relative to the gyroscope scale. The mark42 inscribed on the cover of the level is desirable, since, while thelead 34 is generally visible. it is, to someextent. out of focus, beingdisposed in a plane above that in which the pointer 30 moves.

The box level forms an integral part of the surveying instrument towhich reference has been made. It will be obvious, however, that theindications of the 'box level are not necessary to the carrying out ofthe method herein described. It

is, however, convenient to have this check upon the inclination of thebore hole at the position where the whipstock is set.

The various sections of the drill stem are lined up relative to eachother and the surveying instrument and whipstock by the usual processinvolving the alignment of successive fourbles relative to each other.This may be effected by the well known procedure of attaching targets tothe bottoms and tops of the fourhles and sighting these targets,successively moving them upwardly in steps as, the drill stem is loweredby fourble lengths. The drill stem may be turned to secure properalignment, or, alternatively, the misalignment may be noted andcorrection made. process may be carriedout either by sighting targetsattached to the fourble lengths or by clamping to the fourble lengthstelescopes or other sighting instruments directed towards fixed distantobjects. This method of orientation of the various lengths to secure aknown alignment throughout the entire length of the drill stem is wellknown and the specific steps involved need not be described herein indetail. It is the same procedure as is frequently followed in makingwell surveys which, however. as pointed out above. are usually erroneousdue t'o the neglect of the effects of tortuosity of the bore hole. Ifthe hole is initially properly surveyed with a reliable instrument andtortuosity accounted for, 'then such errors do not enter into thesetting of the whipstock.

By the continuation of this process until the whipstock is at thedesired depth within the bore hole. there is known the relationship ofthe whipstock to the uppermost fourble for a condition of a straightdrill stem; in other words, there is known in theory a line such as thatindicated at e of Fig. l. As a matter Jf fact, however, due totortuosity, the whipstock will be in a position varying from thatcorresponding to a straight supporting stem by an amount correspondingto the angle given by the above formula following a correction ifnecessary for intercardinal error.

It is desirable at this time to move the drill stem upwardly anddownwardly several times to take out any torsional stresses duetofriction during its downward passage during which it would probably beturned. This should be done while very carefully maintaining theorientation by sighting as indicated above.

The drill stem is then turned in a horizontal direction to bring thewhipstock to proper position, the turning being such as to correct forthe calculated deflection due to tortuosity. The drill stem is thenagain moved upwardly and downwardly a number of times to insure theabsence of torsional stresses while the new orientation is maintained bysighting. There is now assurance thatthe whipstock is located in itsproper position.

In the meantime, the surveying instrument continues to operate to recordthe actual position of the whipstock, the instrument, as in the patentnoted above, being provided with a timepiece which is photographedtogether with the other instruments so that those records made followingthe ilnal positioning of the whipstock can be definitely ascertained. Aslow timing device is desirably used, in view of the fact that thesetting of the whipstock takes considerable. time. so that theproduction of an excessive number of records is avoided. This alsoserves to relieve the drain upon the batteries, which are then requiredprimarily to furnish only the relatively small amount of currentnecessary for continuous operation of the gyroscope.

The drill stem is now maintained in its fixed azimuthal position andsetting of the whipstock is efected. In the use of the type of whipstockshown in the drawing, this is accomplished merely by forcing the bottomend into the soil at the bottom of the bore h'ole; or, if the bore holehas been partially filled with cement, then into such cement. If anothertype of ywhipstock is used, securing of. the .whipstock in position isaccomplished in the suitable fashion. The securing of the whipstockin-place may initially be temporary, more permanent securing thereofbeing obtained by cementing.

After permanent or temporary fixation of the whipstock is obtained, thedrill stem is pressed downwardly with sufficient force to shear off therivet or pin 6, leaving the whipstock free of the lower end of the drillstem. which is then withdrawn, bringing up the surveying instrument. Therecords of the surveying instrument may then be examined to determinewhether the whipstock actually has the proper position. Following thecheck of this position, drilling may be resumed in any of the usualfashions, for example, as described 'fully in the article referred toabove.

Various details of manipulation need not be described here since theyare well known and are brought out, for example, in said article. Ii'the deflection is to take place not in the bottom oi' a bore hole but atsome intermediate positcn for lthe purpose, for example, of formingbranches, then the various procedures specified in the article may beused to secure the positioning of the whipstock at the proper location.

The advantages of the present method are primarily inthat it makespossible the correct and accurate setting of a whipstock in a convenientand rapid fashion. The setting ot the whipstock is checked and itsdirection photographicahy recorded in one round trip of the drill stem.`A considerable expense is saved by avoiding a second trip into the holewith a surveying instrument for the purpose of checking the orientationof the whipstock.

It will be clear that variations in the practice of the invention may bemade without departing from its scope as defined by the followingclaims.

What I claim and desire to protect by Letters Patents is:

l. The method of orienting a whipstock within a borehole includingaccurately surveying the bore hole to determine its path; lowering thewhipstock into the bore hole by means of a sectional drill stem, thesections of which are lined up relatively to each. other, and thewhipstock being rigidly connected to said sections; orienting the upperend of the drill stem while making allowance for tortuosity oi the borehole to thereby bring the whipstock into a predetermined position;fixing the whipstock in such position; and then withdrawing the drillstem.

2. The method of orienting a whipstock within a bore hole includingaccurately surveying the bore hole to determine its path; lowering thewhipstock intn the bore hole by means of a sectional drill stem, thesections of which are lined up relatively to each other, and thewhipstock being rigidly connected to said sections, there be ing loweredwith the whipstock aninstrument arranged to indicate the azimuthalposition of the whipstock, the instrument being adjacent the whipstockand attached thereto; orienting the upper end of the drill stem whilemaking allowance tor tortuosity of the bore hole to thereby bring thewhipstock into a predetermined posiinclusive, strike out the formula andinsert insteadmatthieu-reset.

tion; recording the azimuthal position of the I whipstock in saidpredetermined position by means oi' said instrument; fixing theAwhipstock in such position; and then withdrawing the drill stem.

3. The method of orientinga whipstock within a bore hole includingaccurately surveying the bore hole to determine its path; lowering thewhipstock into the bore hole by means oi a seotional drill stem, thesections of which are lined up relatively to each other, and thewhipstock being rigidly connected to said sections; orienting the upperend o! the drill stem while making allowance for tortuosity of the borehole to thereby bring the whipstock into a predetermined position, thedrill stem being moved up and down during the orienting process toremove torsional stresses; ilxing the whipstock in such position; andthen withdrawing the drill stem.

4. The method of orienting a whipstock within a bore hole includingaccurately surveying the bore hole to determine its path; lowering. thewhipstock into the bore hole by means of a sectional drill stem, thesections of which are lined up relatively to each other, and thewhipstock being rigidly connected to said sections, there being loweredwith the whipstock an instrument arranged to indicate the azimuthalposition of the whipstock, the instrument being adjacent the whipstockand attached thereto; orienting the upper end o! the drill stem whilemaking allowance for tortuosity of the bore hole to thereby bring thewhipstock into a predetermined position, the drill stem being moved upand down during the orienting process to remove torsional stresses:recording the azimuthal position of the whipstock in said predeterminedposition by means of said instrument; fixing the whipstock in suchposition; and then withdrawing the drill stem.

' GOTIDANK L. KOTHNY.

July 2, 1935.

hat error appears in the printed specihation'of the above Page 2, firstcolumn, lines 47 to 5l and that the 'said Letters Patent same mayconform to the record should be ma with this ttr'rtttith therein thatthtI of the case in the Patent Oiiioe.

Signed and sealed this 1st day of otober, A. D. 1935.

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msnm mazza, attinghmmttmtfratm.

cerun of common A Patent No. 2,006,556. l July 2, 1935.

. GOTTDANK L. KOTHNY It is hereby certified that error appears in theprinted specicgtion'of the'above numbered patent requiring correction asfollows: Page 2, first coliimn, lines 47 to 51 inclusive, strike out theformula and insert insteadand that thesaid Letters Patent should be readwith this correction therein that the same may conform to the record ofthe case in the Patent Oice.

Signed and sealed this 1st day of October, A. D. 1935'.

[sun] LESLD?. FRAZEB, Acting Commissioner of Patents.

